Burners for furnaces



Sept. 23, 1969 T. map 3,468,616

BURNERS FOR FURNACES Original Filed Dec. 22, 1966 INVENTUR Tammi. \alnno BY Gnu Mk flTTORNEKS United States Patent 3,468,616 BURNERS FOR FURNACES Trevor Ward, London, England, assignor to Hotwork Limited, London, England Original application Dec. 22, 1966, Ser. No. 603,879. Divided and this application Nov. 24, 1967, Ser. No.

Int. Cl. F2311 11/44, 11/40 US. Cl. 431-166 6 Claims ABSTRACT OF THE DISCLOSURE The present application is a divisional application divided out of my copending application Ser. No. 603,879, filed Dec. 22, 1966.

This invention relates to burners for furnaces, the burner being of the kind having a combustion zone defined by a nozzle adapted to be inserted in an opening in a furnace wall and having fuel gas and air for combustion supplied separately to said combustion zone through concentric orifices, as described, for example, in our British Patent No. 1,000,231.

It is the object of the present invention to provide means for preheating the combustion air supplied to the burner, so as to provide a higher efliciency than is normally obtained.

According to the invention, in a burner for furnaces having a combustion zone defined by a nozzle adapted to be inserted in an opening in a furnace Wall and having fuel gas and air for combustion supplied separately to said combustion zone, the fuel gas being supplied to the burner through a conduit coaxial with the nozzle, and the combustion air being supplied through one series of passages in an annular heat exchanger also surrounding the fuel gas supply conduit, the said heat exchanger having another series of passages through which furnace gases from the furnace are passed in heat-exchanging relation to the combustion air, the heat exchanger comprises a block of refractory material formed with longitudinal bores through which extend tubes of smaller external diameter than the bores, the tubes constituting the said one series of passages and the annular spaces in the bores around the tubes constituting the said other series of passages.

Preferably, the furnace gases are drawn through the heat exchanger by ejector means.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, in which:

The single figure is a longitudinal section through one form of burner according to the invention.

Referring to the drawing, a part of the wall of a furnace is shown at 51, and a burner, generally indicated by the reference numeral 52, is mounted in an opening 53 in the said wall. The burner comprises a nozzle 54 fitting in the opening 53, the nozzle being tubular and having an internal flange 55 at its inner end. A cylindrical block 56 of refractory material abuts against the outer end of the nozzle 54 and has a spigot portion 57 which projects into the nozzle, and a hollow cylindrical member 58 abuts against the outer end of the block 56, the parts being retained in assembled relation by rods 59, bent through 90 ICC at their inner ends to engage in radial cavities in the nozzle 54, and screw-threaded at their outer ends to receive nuts 61 engaging a :metal plate 62 closing the outer end of the hollow cylindrical member 58.

The spigot portion 57 of the block 56 is recessed as shown at 63, and a fuel gas supply pipe 60 is extending co-axially through the hollow member 58 and the block 56 leads into the recess 63. A sleeve 64, clamped between the spigot portion 57 and the flange 55 of the nozzle surrounds a combustion space 65 forming an extension of the recess 63 and separates from the said combustion space an annular cavity 66 in the nozzle, which cavity 66 communicates with the combustion space 65 through radial openings 67.

The hollow cylindrical member 58 includes an outer peripheral wall 68, an annular rear wall 69 extending radially inwardly from said peripheral wall, and a reentrant cup-like portion 71. The space between the peripheral wall 68 and the re-entrant portion 71, together with a space between the end of the said re-entrant portion and the block 56 constitutes a chamber 72, hereinafter called the outlet chamber, and the interior of the re-entrant portion 71, which is closed by the plate 62 constitutes an air supply chamber 73 to which air under pressure is fed through a conduit 74 by a. blower or compressor.

An annular series of longitudinal bores 75 are formed in the block 56, the bores extending from the outer face of the block to positions adjacent its inner end, and being connected, at their inner ends, by radial openings 76 to longitudinal grooves 77 in the outer peripheral surface of the nozzle 54, which grooves extend to the inner end of the nozzle.

Extending through each bore 75 is a tube 78, preferably of metal, the external diameter of the tubes being sub-. stantially less than the diameter of the bores. Each tube 78, at its inner end, extends into a reduced continuation of the bore 75 opening into the annular cavity 66, and at its outer end is connected to the air supply chamber 73. The inner end of each tube 78 is extended into an aperture 86 in a wall portion of block 56, said wall portion separating cavity 66 from passages 75.

A duct 79, opens radially from the outlet chamber 72, and a nozzle 81 mounted in the peripheral wall of the air supply chamber 73, is positioned co-axially with the said duct so that air flowing from the said nozzle 81 produces an injector effect tending to extract gases from the chamber 72.

When the burner is in operataion, fuel gas is supplied through the pipe 58 to the recess 63 and so into the combustion space '65, air from the air supply chamber 73 passes through the tubes into the annular cavity 66, from which it passes radially through the openings 67 into the combustion space 65, the air and fuel gas mixing in the combustion space and burning therein. Air also flows through the nozzle 81, and, since the air in the chamber 73 is under compression, creates an injector effect in the duct 79 which produces suction in the chamber 72. This suction draws hot furnace gases through the grooves 77 and bores 75 into the chamber 72, the said gases giving up heat to the inflowing air in the tubes 78, thus preheating the said air and so increasing the efiiciency of the burner.

The burner described with reference to the drawing is particularly suitable for use when the temperature of the furnace atmosphere is very high.

I claim:

1. A burner for furnaces having a combustion zone defined by a nozzle adapted to be inserted in an opening in a furnace wall, and separate passage means for the supply of fuel gas and air for combustion to said combustion zone, a conduit co-axial with the nozzle and defining the fuel gas supply passage, a plurality of tubes arranged around the said conduit and defining the combustion air supply passage means, a block of refractory material surrounding the said conduit longitudinal passages in the said block, and said tubes extending through said passages with substantial radial clearance therein, said radial clearance providing passages for the flow of furnace gases around said tubes whereby the block, the passages therein and the tubes form a heat exchanger for heating the incoming combustion air.

2. A burner according to claim 1, wherein the said passages, at their ends remote from the combustion chamber, lead into an outlet chamber, ejector means being provided to create suction in said outlet chamber to draw the furnace gases through the passages.

3. A burner according to claim 1, wherein the said passages are closed at their ends adjacent the combustion zone, lateral opening being provided which connect the said passages at that end to longitudinal passage means external to the burner nozzle so that furnace gases traverse said longitudinal passage means before coming into con tact with said tubes.

4. A burner according to claim 1, wherein the combustion zone is surrounded by a sleeve defining an annular space in the nozzle surrounding said combustion zone, wall means separating the said annular space from the passages in the block are formed with apertures to receive the ends of the tubes, and radial apertures are formed in said sleeve for the passage of combustion air to the combustion zone.

5. A burner according to claim 1, wherein the heat exchanger comprises a block of refractory material formed with longitudinal bores through which extend tubes of smaller external diameter than the bores, the tubes constituting the said one series of passages and the annular spaces in the bores around the tubes constituting the said other series of passages.

6. A burner according to claim 5, wherein the bores are closed at one end and are connected at that end by lateral openings to longitudinal grooves in the outer peripheral surface of the burner nozzle, the said bores being open at their other ends to an outlet chamber, and wherein the tubes extend through the closed ends of the bores into the burner nozzle and through the open ends of the bores across the annular chamber to an air supply chamber, ejector means being provided in the annular chamber to draw the furnace gases through the bores in heat-exchanging relation with air in the tubes.

References Cited UNITED STATES PATENTS 1,724,783 8/1929 Smallwood et al. 263-9 3,163,202 12/1964 Schmidt et a1 431166 3,174,526 3/1965 Von Linde 431-116 3,361,183 1/1968 Reichhelm 431-116 FREDERICK L. MATIESON, JR., Primary Examiner ROBERT A. DUA, Assistant Examiner US. Cl. X.R. 431-215 

